måndag 3 februari 2014

Theory of Relativity from Relativity of Simultaneity

In recent posts we have seen that the theory of relativity, one of the two pillars of modern physics the other being quantum mechanics, came out of a theoretical study of clock synchronization for observers moving with respect to each other, a study initiated by Lorentz and Poincare and picked up by Einstein, leading to the insight that absolute synchronization with absolute simultaneity was impossible in full generality.

Because of the finite speed of light, observers at different locations and different velocities would not be able to agree on an objective common timing of all events, and thus physicists would have to accept relativity of simultaneity as the root of relativity theory and thus be forced to give up the idea of absolute time (and space) as the basis of classical Newtonian mechanics, and then bravely enter into modern physics.

So, the great achievement of Einstein consists in discovering that the concept of simultaneity is a concept . . . that we have to define. People had the knowledge of space, the knowledge of time, had this knowledge many centuries, but nobody guessed that idea.

and Weyl:

We are to discard our belief in the objective meaning of simultaneity; it was the great achievement of Einstein in the field of the theory of knowledge that he banished this dogma from our minds.

Einstein inspired by Poincare and Lorentz thus posed a question nobody had found any reason to ask before him, namely if a universal system of clock synchronization could be set up, and then gave the answer that this would be difficult in full generality and as a result the dogma of classical Newtonian absolute space and time suddenly had to be "banished from our minds".

This made Einstein into the most grandios physicist all times. One thing is to discover and describe new physics, another is to root out wrong conceptions of the world from our minds. This connects to the quote of the Swedish writer and philosopher Thomas Thorild imprinted in stone over the entrance to the main hall of Uppsala University: To think freely is grand, but to think correctly is even grander.

Alice's Adventures in Wonderland was published in 1865 under the pseudonym Lewis Carroll by the mathematician and writer Charles Lutwidge Dodgson, and predated with the White Rabbit's I'm late, I'm late, I'm late, both Poincare and Einstein by giving evidence of the impossibilty of absolute simultaneity. This connects to the time dilation of special relativity with the clock of an observer running away from us appearing (to us) to run slow.